Documentation

Specify a Function Handle

Function handles provide a way to represent a function as a variable. The function must be a local or nested function in the same file as the app code, or you can write it in a separate file that is on the MATLAB path.

To create the function handle, specify the @ operator before the name of the function. For example, this uicontrol command specifies the Callback property to be a handle to the function pushbutton_callback:

b = uicontrol('Style','pushbutton','Callback',@pushbutton_callback);

Here is the function definition for pushbutton_callback:

function pushbutton_callback(src,event)
   display('Button pressed');
end

A benefit of specifying callbacks as function handles is that MATLAB checks the function for syntax errors and missing dependencies when you assign the callback to the component. If there is a problem in the callback function, then MATLAB returns an error immediately instead of waiting for the user to trigger the callback. This behavior helps you to find problems in your code before the user encounters them.

Specify a Cell Array

Use a cell array to specify a callback function that accepts additional input arguments that you want to use in the function. The first element in the cell array is a function handle. The other elements in the cell array are the additional input arguments you want to use, separated by commas. The function you specify must define the same two input arguments as described in Specify a Function Handle. However, you can define additional inputs in your function declaration after the first two arguments.

This uicontrol command creates a push button and specifies the Callback property to be a cell array. In this case, the name of the function is pushbutton_callback, and the value of the additional input argument is 5.

b = uicontrol('Style','pushbutton','Callback',{@pushbutton_callback,5});

Here is the function definition for pushbutton_callback:

function pushbutton_callback(src,event,x)
   display(x);
end

Like callbacks specified as function handles, MATLAB checks callbacks specified as cell arrays for syntax errors and missing dependencies when you assign the callback to the component. If there is a problem in the callback function, then MATLAB returns an error immediately instead of waiting for the user to trigger the callback. This behavior helps you to find problems in your code before the user encounters them.

Specify an Anonymous Function

Specify an anonymous function when you want a UI component to execute a function that does not support the two arguments that are required for function handles and cell arrays. For example, this uicontrol command creates a push button and specifies the Callback property to be an anonymous function. In this case, the name of function is myfun, and its function declaration defines only one input argument, x.

b = uicontrol('Style','pushbutton','Callback',@(src,event)myfun(x));

Specify a Character Vector Containing MATLAB Commands (Not Recommended)

You can specify a character vector when you want to execute a few simple commands, but the callback can become difficult to manage if it contains more than a few commands. The character vector you specify must consist of valid MATLAB expressions, which can include arguments to functions. For example:

hb = uicontrol('Style','pushbutton',...
               'String','Plot line',...
               'Callback','plot(rand(20,3))');

'plot(x)'

Unlike callbacks that are specified as function handles or cell arrays, MATLAB does not check character vectors for syntax errors or missing dependencies. If there is a problem with the MATLAB expression, it remains undetected until the user triggers the callback.